1. Field of the Invention
Diving apparatus of the closed loop push-pull type.
2. Description of the Prior Art
In a push-pull type breathing apparatus system the diver is supplied with breathing gas from a remote source by way of a supply line and exhaled gas is returned back to the source by way of a return line for gas conditioning such as CO.sub.2 removal, oxygen replenishment, etc. In the design of such breathing systems, if one were to collect each discharged breath and measure the total volume discharged in one minute the pumping rate could be determined which, in man, is termed respiratory minute volume (RMV). During hard work, maximum inspiratory or expiratory flows are experienced and these are roughly three times the value of the RMV. Accordingly the hoses and pumps which provide gas to or remove gas from the diver must have three times the capacity if they must meet peak flows rather than RMV flows.
In the field of underwater diving, large volume tanks are sometimes utilized at the remote source to reduce pump requirements on the supply side to that of RMV flows and to smooth flow on the return side. However, even with the volume tanks the gas handling hoses must be large enough to adequately pass peak breathing velocities. In addition volume tanks become more inefficient with increasing depths of operation.
It is accordingly one object of the present invention to provide a system wherein not only pump capacity requirements are reduced but additionally the size and capacity of the gas handling hoses are reduced, an important consideration in that diver umbilicals should be kept as small and as flexible as possible to ease diver movement and to minimize stowage room and handling requirements.
In one type of push-pull system breathing gas is supplied to a diver's helmet and the helmet pressure is controlled by an exhaust control valve. The exhaust control valve discharges into the return line to the remote source. If a diver's task requires him to descend below the level of the remote source then the return umbilical must be designed to withstand a certain pressure differential which can be very significant and requires the provision of relatively stiff hoses from the diving helmet.
It is another object of the present invention to provide a device which will allow the employment of thinner walled, more flexible hoses to the helmet so as to allow greater freedom of movement by the diver.